1. Field of the Invention
This invention relates to a base tube for a fuel cell, whose porosity and pore diameter are increased to improve the power generation characteristics of the resulting fuel cell.
2. Description of the Related Art
FIG. 1 shows the outline of a base tube of a thermal spray type solid electrolyte fuel cell.
A thermal spray type solid electrolyte fuel cell (SOFC), as shown in FIG. 1, is produced in the following manner: A thermit of Ni and yttria-stabilized zirconia (YSZ) is provided in a film form by plasma spraying on a porous cylindrical base tube 1 of calcia-stabilized zirconia (CSZ) to serve as a fuel electrode 2. On this fuel electrode 2, oxygen ion-conductive YSZ is provided in a film form by plasma spraying to serve as an electrolyte 3. On this electrolyte 3, LaCoO.sub.3 is provided in a film form by acetylene flame spraying to serve as an air electrode 4. In this manner, a fuel cell is constructed. Finally, the fuel electrode 2 and the air electrode 4 are connected together in series by an electrically conductive connecting material (interconnector) 5 in a film form composed of a thermit of NiAl and alumina.
The production of a fuel cell by thermal spraying as earlier technology is laborious and costly, and should be decreased in cost. Thus, a co-sinter type fuel cell, which is composed of a base tube, a fuel electrode and an electrolyte sintered integrally, and requires a reduced number of sintering operations, has been developed. However, this type of fuel cell poses the problem of insufficient gas permeability of the base tube for achieving desired power generation characteristics. Under these circumstances, the present invention proposes a base tube for an integral sinter type fuel cell, the base tube having increased porosity and pore diameter to improve the power generation characteristics of the fuel cell.